/*
 *  EnglishLettersValidationMethod.cs
 *  
 *  Validates whether the user input contains English letters only.
 *  
 *  Copyright (c) 2009, Richard Bao Labs.
 *  
 *  The contents of this file are subject to the Mozilla Public License
 *  Version 1.1 (the "License"); you may not use this file except in
 *  compliance with the License. You may obtain a copy of the License at
 *  
 *  http://www.mozilla.org/MPL/
 *  
 *  Software distributed under the License is distributed on an "AS IS"
 *  basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
 *  the License for the specific language governing rights and limitations
 *  under the License.
 *  
 *  The Original Code is RichControlLibrary.
 *  
 *  The Initial Developer of the Original Code is Richard Bao Labs.
 *  All Rights Reserved.
 */

using System;
using System.Collections.Generic;
using System.Text;
using System.Text.RegularExpressions;

namespace RichControlLibrary
{
    /// <summary>
    /// Validates whether the user input contains English letters only.
    /// </summary>
    public sealed class EnglishLettersValidator : RegexValidator
    {
        /// <summary>
        /// Returns a <see cref="Regex"/> instance as the validating regular expression.
        /// </summary>
        /// <returns>A <see cref="Regex"/> used to validate whether the user input contains English
        /// letters only.</returns>
        protected override Regex GetValidatingRegex()
        {
            StringBuilder sb = new StringBuilder();

            sb.Append(@"^[");
            
            if ((_casing & ValidationCasingPolicy.LowercaseOnly) == ValidationCasingPolicy.LowercaseOnly)
            {
                sb.Append(@"a-z");
            }

            if ((_casing & ValidationCasingPolicy.UppercaseOnly) == ValidationCasingPolicy.UppercaseOnly)
            {
                sb.Append(@"A-Z");
            }

            sb.Append(@"]+$");

            return new Regex(sb.ToString());
        }

        private ValidationCasingPolicy _casing = ValidationCasingPolicy.UpperAndLowerCases;
        /// <summary>
        /// Gets or sets whether the uppercase or lowercase is acceptable.
        /// </summary>
        public ValidationCasingPolicy Casing
        {
            get { return _casing; }
            set { _casing = value; }
        }
    }
}
